1. Field of the Invention
The invention relates to a current programming apparatus, an active matrix type display apparatus, and a current programming method. More particularly, the invention is preferably used in an active matrix type display apparatus using current driving type display elements.
2. Related Background Art
In an active matrix type display apparatus using electroluminescent elements, a current writing type circuit for writing and storing a drive current of a light emitting element into a driving circuit of each pixel is used. In the present specification, the operation to write and store the drive current into each pixel of such a matrix type display apparatus is called a current programming and a circuit for the current programming is called a current programming circuit.
A current programming circuit to hold a current which is supplied to a data line as a gate-source voltage of a transistor has been disclosed in FIG. 18 of the U.S. Publication No. 2002195964. Such a Patent Document discloses that when data is written into the current programming circuit, by supplying the current in the direction in which the write current is set off, gradation displays of black and low luminance level can be improved.
When the conventional current writing type pixel circuit is used, there is a case where the writing operation of an image data current cannot be stably executed in each pixel circuit. Although it will be explained in detail hereinbelow, it is because a threshold value of a driving transistor varies every pixel.
It is an object of the invention to provide a current programming apparatus, an active matrix type display apparatus, and their current programming method in which the writing operation of an image data current can be stably executed.